This invention relates to an ultrasonic transducer which radiates ultrasonic waves into the body of a patient and detects echoes reflected from, for example, the internal organs of the patient, and a method of manufacturing the same.
FIGS. 1 and 2 show the conventional ultrasonic transducers. The transducers are constructed by arranging a plurality of ultrasonic transducer elements on an ultrasonic wave absorber 12 in first and second directions. The probe 10 of FIG. 1 comprises a plurality of transducer elements which are set side by side in the array direction 2 and extend in a direction 4 perpendicular to the array direction 2. The transducer element 14 comprises a piezoelectric element and electrodes 16, 18 respectively baked to the upper and lower planes of said piezoelectric element, said lower plane facing the ultrasonic wave absorber. A ground electrode 20 is, for example, soldered to all the electrodes 16 to render them conductive. Lead lines 22 are, for example, soldered to the electrodes 18.
In the conventional ultrasonic transducer 24 of FIG. 2, the transducer element 14 is divided into three parts (transducer element groups 14a, 14b, 14c) which are arranged in the indicated direction 4. Ground electrodes 20a, 20b, 20c respectively connect the transducer element groups 14a, 14b, 14c which are set side by side in the array direction 2.
The conventional ultrasonic transducer 10 of FIG. 1 is characterized in that signals sent forth from the transducer elements 14 are controlled to have their phases changed for each transducer element, thereby elevating the directionality with respect to the array direction 2. With the probe 10, however, the direction of the signals can be controlled only with respect to said array direction 2. Conversely, with the conventional ultrasonic transducer 24 of FIG. 2, the phases of the signals set forth from the transducer elements 14 can have their phases controlled with respect to both directions 2 and 4, thereby enabling ultrasonic waves issued from the transducer to be converged in the form of a round conical shape.
The conventional ultrasonic transducer 24 of FIG. 2 whose transducers are arrayed in two directions, namely, in the lattice form, is manufactured in the following manner. The first manufacturing method comprises the following steps. A lead line 22 is welded to the underside of each of the transducer element groups 14a, 14b, 14c. These transducer elements are equidistantly fixed to the surface of the ultrasonic wave absorber 12 so as to be arranged in the array direction 2. Ground electrodes 20a, 20b, 20c each formed of a thin metal sheet are, for example, soldered to the corresponding groups 14a, 14b, 14c of the transducers. The second manufacturing method comprises the following steps. A plate transducer material having substantially the same size as the plane of the ultrasonic wave absorber 12 is provided. Lead lines 22 are welded to those portions of the underside of said plate transducer material which correspond to the set positions of the transducer elements belonging to the groups 14a, 14b, 14c. After the plate transducer material now provided with lead lines 22 is adhered to the ultrasonic wave absorber 12, notches extending in the directions 2 and 4 are equidistantly cut out in the surface of said plate transducer material (sgl) to provide three groups of transducer elements 14a, 14b, 14c. Thereafter, ground electrodes 20a, 20b, 20c are welded to the corresponding groups 14a, 14b, 14c of transducer elements.
The above-mentioned, first manufacturing method is accompanied with the drawback that difficulties are presented in arranging numerous transducer elements in the array directions 2 and 4 at an accurate equal distance. The second manufacturing method is also unsatisfactory in that it is difficult to solder numerous lead lines to the plate transducer material at a prescribed distance, and further, the lead lines are likely to be broken when said plate transducer material is notched. In both first and second manufacturing methods, it is necessary to draw out the numerous lead lines welded to the underside of said plate transducer material by letting them penetrate the holes formed through the ultrasonic wave absorber 12 or by letting said lead lines extend through grooves cut out in the welded plane of said ultrasonic wave absorber 12. Such a step unavoidably gives rise to structural complexities. This drawback becomes more noticeable, as the transducer element is further miniaturized and a larger number of lead lines are applied. As a result, difficulties are present in the treatment of the terminals of the groups of lead lines and their proper arrangement, thereby hindering the manufacture of an ultrasonic transducer in the miniaturized form. The above-mentioned circumstances hinder the dissemination of the technology of manufacturing an ultrasonic transducer whose transducers are arranged in two array directions and which offer various advantages in ultrasonic diagnosis.